linux-kernel - Re: [RFC v3 1/2] kernel/sysctl: support setting sysctl parameters from kernel command line

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Message-ID: <202003262048.70D845CDF@keescook>
Date:   Thu, 26 Mar 2020 20:50:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-mm@...ck.org, Ivan Teterevkov <ivan.teterevkov@...anix.com>,
        Michal Hocko <mhocko@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Guilherme G . Piccoli" <gpiccoli@...onical.com>
Subject: Re: [RFC v3 1/2] kernel/sysctl: support setting sysctl parameters
 from kernel command line

On Thu, Mar 26, 2020 at 11:08:40PM +0100, Vlastimil Babka wrote:
> On 3/26/20 9:24 PM, Kees Cook wrote:
> I didn't want to modify param for the sake of error prints, but perhaps
> the replacements won't confuse system admin too much?

Ah, fair enough. Should be fine to do it against "path" then. Ignore
that bit from me. ;)

> >> +	filp_close(file, NULL);
> > 
> > Please check the return value of filp_close() and treat that as an error
> > for this function too.
> 
> Well I could print it, but not much else? The unmount will probably fail
> in that case?

Maybe? This is just a nit of mine from tracking horrible bugs that
turned out to be unreported 'close' failures. :)

> But I guess the "mount on first applicable argument" approach would work
> with this scheme as well:
> 
> struct vfsmount *proc_mnt = NULL;
> parse_args(..., &proc_mnt, ...)

Yes please! That would be perfect. (And yeah, it's a sensible
optimization to do it "as needed"; I hadn't thought of that.)

-- 
Kees Cook